Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-692, 2017 Manuscript under review for journal Hydrol. Earth Syst. Sci. Discussion started: 16 February 2017 c Author(s) 2017. CC-BY 3.0 License. Water resources in the Badain Jaran Desert, China: New insight from isotopes Xiujie Wu 1, 2, 3, Xu-Sheng Wang1, Yang Wang 2, 3, 4,*, Bill X. Hu 1, 2, 4,* 1School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing, 100083, P. R. China 5 2Department of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, FL, 32304, USA 3High National Magnetic Field Laboratory, Tallahassee, FL, 32310, USA 4Institute of Groundwater and Earth Sciences, The Jinan University, Guangzhou, Guangdong Province, 510632, P. R. China Correspondence to: Yang Wang (
[email protected]); Bill X. Hu (
[email protected]) Abstract. To better understand the origin of water in the Badain Jaran Desert, China, water samples were collected from 10 lakes, a spring and local unconfined aquifer for analyses of radiocarbon (14C) and tritium (3H), stable hydrogen and oxygen isotope ratios (δ2H, δ18O), and d-excess values (=δ2H – 8δ18O). A series of evaporation experiments were also conducted in the desert to examine how the isotopic signature of water may change during evaporation and infiltration under local environmental conditions. The results show that the lakes in the southeastern sand dune area are fed by groundwater discharging into the lakes and that local groundwater, on the other hand, is derived primarily from modern meteoric 15 precipitation in the region. Although dissolved inorganic carbon (DIC) in groundwater yielded very old radiocarbon ages, the presence of detectable amounts of tritium in groundwater samples, together with their δ2H, δ18O and d-excess characteristics, strongly suggest that the old radiocarbon ages of DIC do not represent the residence time of water in the aquifer but are the result of addition of old DIC derived from dissolution of ancient carbonates in the aquifer.